Multilevel power converter

• US 9,106,074 B2
• Filed: 02/13/2013
• Issued: 08/11/2015
• Est. Priority Date: 04/02/2012
• Status: Expired due to Fees

• Current Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Takizawa, Satoki
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Tiku, Sisay G
• Application Number:
  US13/765,903
• Publication Number:
  US 20130258728A1
• Time in Patent Office: 909 Days
• Field of Search: 363/43, 363/50, 363/55, 363/56.01, 363/56.02, 363/56.05, 363/71, 363/131
• US Class Current: 1/1
• CPC Class Codes: H02H 7/1203 Circuits independent of the type of conversion
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: H02M 7/797 using semiconductor devices only

Abstract

Aspects of the invention address a circumstance in multilevel power converter devices having a bidirectional switch connected to a middle point of a DC power supply assembly, whereby interruption of the device may cause break down of semiconductor switches due to overvoltage if the semiconductor switches are totally interrupted simultaneously. In some aspects, a shut down procedure of a multilevel power converter device having a bidirectional switch connected to the middle point of a DC power supply assembly, gates of semiconductor switches are interrupted one by one according to a predetermined sequence or a sequence corresponding to the conditions of voltage and current at that moment with a time interval, and finally the bidirectional switch connected to the middle point of a DC power supply assembly is interrupted. As a result, a transition from an operating state to a shut down state can be made with minimum voltage variation.

Claims

1. A multilevel power converter, for converting DC power to AC power or AC power to DC power, comprising:

a DC power supply assembly having a positive terminal, a negative terminal, and a middle point terminal at a middle electric potential between the positive terminal and the negative terminal; and

a circuit for one phase including;

a series-connected semiconductor switch circuit of at least four semiconductor switches each having an antiparallel-connected diode, the series-connected semiconductor switch circuit being connected between the positive terminal and the negative terminal of the DC power supply assembly,

a bidirectional switch capable of bidirectional switching connected between the middle point terminal of the power supply assembly and an intermediate connection point of the series-connected semiconductor switch circuit, and

a circuit including a one or more semiconductor switches connected between each of two output terminals outputting a potential of each connection point of the semiconductor switches in the series-connected semiconductor switch circuit and a terminal of the bidirectional switch, the terminal being at a side unconnected to the DC power supply assembly, and

a capacitor connected between the two output terminals;

wherein the multilevel power converter responds to a request for a total phase interruption for forced shut down in a procedure of interrupting the semiconductor switches according to a predetermined sequential operation and finally interrupting the bidirectional switch.

2. The multilevel power converter according to claim 1, wherein

the sequential operation to interrupt the semiconductor switches is carried out one by one with a predetermined time interval between interruption processes of each of the switches in an ON state.

3. The multilevel power converter according to claim 1, wherein the multilevel power converter includes five or more levels of power converter.

4. The multilevel power converter according to claim 2, wherein the multilevel power converter includes five or more levels of power converter.